This invention relates to the invention described and claimed in co-pending U.S. patent application Ser. No. 652,386, filed Sept. 20, 1984, which is hereby incorporated by reference in its entirety. The present invention relates to a lancet assembly, and more particularly to such an assembly which provides automatic retractable lancet movement, utilizing resilient means incorporated into the assembly having the dual function of damping the lancet drive movement, together with providing the automatic retraction of the lancet once the puncture is made.
Sharp-pointed lancets have been employed for many years to make a quick puncture or penetration of a patient's skin in order to provide a small outflow of blood. Various tests may be employed with only a small amount of blood so that the blood flowing from a finger prick is normally sufficient to carry out a substantial number of tests. However, due to the sensitive nerve endings in the fingertip area, this procedure sometimes induces a significant amount of pain in the patient, even though the skin puncture produces minimal cutting. Moreover, as will be understood, many people are freightened by the appearance of a blade or skin puncture apparatus of any kind wherein the cutting portion is available for them to see prior to the puncture. In order to minimize potential pain, as well as reduce apprehension in a patient, it is desirable to make the thrust of the lancet through the patient's skin rapidly and to provide a rapid withdrawal and shielding of the lancet blade itself.
Other problems involved with such procedures include contamination of the technician in the procedures involved in taking the blood sample. That is, the patient may have some disease, and if the lancet blade which has carried out the puncture action should prick the skin of a technician subsequent to the initial puncture, the technician and/or nurse and/or doctor involved may be exposed to contamination. Thus, it is important to have automatic retraction of the blade immediately after puncture so that the blade is not exposed for an accidental puncture of someone else's skin.
Spring-loaded lancets of different types and forms have been well known and are typified, for example, by U.S. Pat. Nos. 55,620; 1,135,465; 3,030,959; 4,139,011; 4,203,446; 4,230,118; 4,449,529 and 4,88,925.
U.S. Pat. No. 4,203,446, noted above, is significant in that it teaches the puncture of the skin of a patient with a lancet which is retracted back into the device after piercing the patient's skin. In the patented device, the downward motion of the lancet is initiated by impact of a spring-loaded hammer, and as this motion continues the spring potential decreases. At the time of the impact, the return spring begins to compress and increase potential energy. When the potential energy in the return spring under compression exceeds the potential energy in the driving spring, compression of the return spring ends and decompression begins. This, then reverses the motion of the lancet.
However, impact is necessary to compress the return spring and increase its potential energy rapidly. Without the impact force, the spring forces would approach equilibrium and then there would be no reverse motion in order to retract the lancet out of the patient's skin. Moreover, since spring potential is critical in this patented device, a conical spring is relied upon to overcome recoil due to the surge of the larger return spring. Other problems include, of course, the cost of such an involved assembly. Despite the foregoing inventions, improvements in this field of lancets are still being sought.
With this invention, by contrast, an improved automatic retractable throw-away lancet assembly is provided which is relatively simple of construction and easily moldable into two pieces of plastic material. Nevertheless, this simple construction provides, through the utilization of two annular abutments on a lancet holder body assembly cooperating with a single annular integral abutment on a lancet holder guide, a snap action drive for the lancet to rapidly drive the lancet for the puncture action, with an automatic retraction of the lancet once the puncture has been completed. Moreover, a single, conventional coil spring is utilized which first provides a damping of the lancet drive, once the cooperating abutments provide the snap action, and, secondly, provides automatic retraction of the lancet.
In accordance with principles of the present invention, the desired functions are achieved by virtue of a very simplified three-piece structure including a lancet holder guide comprised of a simple elongated piece of semi-rigid material such as a plastic formed into an elongated body having a passage therethrough. Movable in the passage is an elongated lancet holder assembly arranged to have an integral activation handle at one end thereof, and an arrangement for connection of a lancet on the opposite end.
The lancet holder body assembly includes two spaced integral ridges around the perimeter thereof forming abutments. A simple coil spring is mounted between the lancet holder guide and the lancet holder assembly itself. The abutments cooperate with a single integral abutment around the internal perimeter of the lancet holder guide or housing for holding the two parts together prior to use, for providing the snap action in the drive of the lancet to provide the desired puncture, and for providing a stop in both directions of movement of the lancet holder. These two molded pieces together with the spring and the actual lancet blade provide an appropriate and accurate skin puncture for obtaining the desired quantity of blood for carrying out appropriate tests. Moreover, the arrangement is such that it may be immediately discarded without any danger of contamination by subsequent puncture of those who may handle the used lancet assembly. Nevertheless, even though the structure provides the several desired functions of a modern lancet in use, it is easily manufactured by conventional molding procedures.
Other objects and advantages of this invention will be apparent from the following description, the accompanying drawings and the appended claims.